Convert references to FileSystem & Co. into shared pointers (avoid use after free)

src/FileSystemJsObject.cpp

Index: src/FileSystemJsObject.cpp
===================================================================
--- a/src/FileSystemJsObject.cpp
+++ b/src/FileSystemJsObject.cpp
@@ -20,17 +20,17 @@ namespace
     IoThread(JsEngine& jsEngine, JsValuePtr callback)
       : jsEngine(jsEngine), fileSystem(jsEngine.GetFileSystem()),
         callback(callback)
     {
     }
 
   protected:
     JsEngine& jsEngine;
-    FileSystem& fileSystem;
+    FileSystemPtr fileSystem;
     JsValuePtr callback;
   };
 
   class ReadThread : public IoThread
   {
   public:
     ReadThread(JsEngine& jsEngine, JsValuePtr callback,
                const std::string& path)
@@ -39,17 +39,17 @@ namespace
     }
 
     void Run()
     {
       std::string content;
       std::string error;
       try
       {
-        std::tr1::shared_ptr<std::istream> stream = fileSystem.Read(path);
+        std::tr1::shared_ptr<std::istream> stream = fileSystem->Read(path);
         content = Utils::Slurp(*stream);
       }
       catch (std::exception& e)
       {
         error = e.what();
       }
       catch (...)
       {
@@ -81,17 +81,17 @@ namespace
 
     void Run()
     {
       std::string error;
       try
       {
         std::tr1::shared_ptr<std::ostream> stream(new std::stringstream);
         *stream << content;
-        fileSystem.Write(path, stream);
+        fileSystem->Write(path, stream);
       }
       catch (std::exception& e)
       {
         error = e.what();
       }
       catch (...)
       {
         error = "Unknown error while writing to " + path;
@@ -119,17 +119,17 @@ namespace
     {
     }
 
     void Run()
     {
       std::string error;
       try
       {
-        fileSystem.Move(fromPath, toPath);
+        fileSystem->Move(fromPath, toPath);
       }
       catch (std::exception& e)
       {
         error = e.what();
       }
       catch (...)
       {
         error = "Unknown error while moving " + fromPath + " to " + toPath;
@@ -157,17 +157,17 @@ namespace
     {
     }
 
     void Run()
     {
       std::string error;
       try
       {
-        fileSystem.Remove(path);
+        fileSystem->Remove(path);
       }
       catch (std::exception& e)
       {
         error = e.what();
       }
       catch (...)
       {
         error = "Unknown error while removing " + path;
@@ -195,17 +195,17 @@ namespace
     }
 
     void Run()
     {
       std::string error;
       FileSystem::StatResult statResult;
       try
       {
-        statResult = fileSystem.Stat(path);
+        statResult = fileSystem->Stat(path);
       }
       catch (std::exception& e)
       {
         error = e.what();
       }
       catch (...)
       {
         error = "Unknown error while calling stat on " + path;